Environ. Sci. Technol. 1997, 31, 518-522
Application of NMR Spectroscopy to Environmental Analysis: Detection of Trace Amounts of Chemical Warfare Agents and Related Compounds in Organic Extract, Water, and Sand MARKKU T. MESILAAKSO Finnish Institute for Verification of the Chemical Weapons Convention, P.O. Box 55, FIN-00014 University of Helsinki, Finland
1H and 31P{1H} NMR spectroscopy were used in the identification of chemical warfare agents and related compounds present in trace amounts in organic extract, water, and sand samples. The work was done as part of an international Trial Proficiency Test of laboratory performance. NMR spectroscopy provided identification of bis(2chloroethyl)ethylamine (HN-1) in an organic extract and identification of methylphosphonic acid, cyclopentyl methylphosphonate, ethyldiethanolamine, diethylaminoethanol, and bis(N,N-diethylaminoethyl)disulfide in samples of canal water. Supporting evidence was provided for the presence of O-cyclopentyl S-2-(diethylamino)ethyl methylphosphonothiolate in the organic extract and of ethyldiethanolamine and diethylaminoethanol in a sand sample. The sample preparations, experiments, spectral analyses, and results obtained by NMR spectroscopy are described.
Introduction Participants in the international interlaboratory comparison (round-robin) tests for the verification of chemical disarmament have selected NMR spectroscopy as one of the three best instrumental techniques for the identification of chemical warfare (CW) agents and related compounds (1-3). Samples in the tests have included air, soil, water, rubber, paint, and concrete and wipe, liquid, and solid samples collected from reactors, pipelines, storage containers, and aqueous and organic wastes of chemical facilities. Compounds spiked to the samples have included CW agents, their precursors and degradation products, and other relevant compounds. The aim of the tests has been the development and testing of methods of sample preparation and analysis (4, 5), with emphasis on qualitative analysis and a requirement for unambiguous identification. Our laboratory begins by screening all samples by gas chromatography (GC), with element-specific detection (N, P, S) and retention index monitoring. The analytical techniques are gas chromatography in combination with lowresolution mass spectrometry in electron ionization (GCMS/EI) and chemical ionization (GC-MS/CI) modes; MS/ MS and high-resolution mass spectrometry (HRMS); NMR spectroscopy in proton, phosphorus-31, fluorine-19, and carbon-13 observation; and gas chromatography-Fourier transform infrared spectroscopy (GC-FTIR). The analytical procedures that are followed are described in the Recommended Operating Procedures (ROP) as upgraded after the * Corresponding author e-mail address: markku.mesilaakso@ helsinki.fi.
518
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 31, NO. 2, 1997
methods development phase (6). Figure 1 shows a scheme of the general analytical procedure including the sample preparations and collaborative use of all analytical methods. Identification of a compound whose reference data or spectra are included in databases requires consistent results obtained by at least two different techniques except for the combination GC-MS/EI and GC-MS/CI, which is able to stand alone. Because derivatizations are not required, sample preparation is simpler in NMR spectroscopy than in analytical methods relying on GC as inlet technique. Compound identification by NMR is made through reference to spectra (1H, 13C{1H}, 19F, 31P{1H}, and/or 31P) included in a spectrum library (7), through comparison with a spectrum of the authentic compound, or through spiking the test sample with an authentic compound (6). 19F and 31P NMR also allow screening for fluorine- or phosphorus-containing chemicals. Due to the low sensitivity of carbon-13, recording of 13C{1H} spectra may be futile in concentration below 100 µg/mL. By way of comparison, the detection limit of a compound when 1 H is observed at 400 MHz or 19F at 376 MHz may be as low as 1 µg/mL (1 ppm). One or two orders more of the analyte is required for phosphorus observation. Two-dimensional correlation techniques may be applied to support the analysis (8, 9). Where insufficient data are obtained, the resonances revealed may be a useful support to identifications based on other analytical techniques (10, 11). With NMR, no direct on-line method exists to separate trace amounts of individual compounds from the background and solvent compounds that always are present in a sample prepared from an environmental matrix. The solvent and the pH value may significantly affect the resonances of analytes and compounds of the matrix, which means that the solvent and the pH should be the same in the authentic reference sample, test sample, and blank sample. At the same time, changes in solvent, pH, or the sample temperature (12) may help in distinguishing important resonances from the overlapping ones. In NMR, therefore, the procedure selected for sample preparation and the optimization of the subsequent experiments are considered of critical importance. In a previous report (12), we described the sample preparation for NMR, the NMR experiments, and the identification by NMR of compounds relevant to the Chemical Weapons Convention (CWC) (13) that were spiked in paint, rubber, and soil matrices. That work was done in connection with the first Trial Proficiency Test (January 1995) coordinated by the Preparatory Commission for the Organisation for the Prohibition of Chemical Weapons/Provisional Technical Secretariat (OPCW/PTS). The present paper describes the analysis by NMR of organic extract, water, and sand samples carried out by our laboratory in the second Trial Proficiency Test (May 1995). The purpose of the test was the identification of the scheduled chemicals (13) and their degradation products.
Experimental Section The sample matrices were 4 mL of acetonitrile extract (E; intended to mimic an extract from a wipe or material sample), two 50-mL portions of canal water (W-1 and W-2), and 50 g of sand (S) spiked with 5-10 ppm of two or three relatively high-boiling compounds related to the CWC or to the test scenario. Some of the matrices were also spiked with diesel fuel or polyethylene glycol to produce an interfering background. A designated blank (EB, WB, SB) was provided with each of the sample matrices. The spiking information is given in Table 1. The spectra were recorded on a Bruker AMX-400 NMR spectrometer equipped with a 5-mm P/F dual or a quattro nucleus probe head (observable nuclei: 1H, 13C, 19F, 31P).
S0013-936X(96)00352-5 CCC: $14.00
1997 American Chemical Society
FIGURE 1. General procedure for the identification of compounds in a test sample. Identifications are made by different spectrometric methods with the aid of data libraries and authentic reference compounds. Before the test began, the spectrometer performance was checked for both probe heads with line shape and sensitivity tests. The probe heads were selected so as to obtain best sensitivity in proton and phoshorus-31 observation. The P/F dual probe head can be tuned for proton observation so as to provide good signal-to-noise ratio, S/N 250:1 from 0.1% ethylbenzene; also the sensitivity for fluorine-19 observation is high: S/N 310:1 from 0.05% trifluorotoluene. The quattro nucleus probe head provides the highest sensitivity for phosphorus-31 observation, S/N 130:1 from 0.0485 M triphenyl phosphate. The sample temperatures were set to 27.0 °C. Tetramethylsilane (TMS, δ ) 0.0 ppm) and 3-(trimethylsilyl)propionic-2,2,3,3-d4 acid sodium salt (TSP-d4, δ ) 0.0 ppm) served as external chemical shift references in proton spectra, and 85% H3PO4 (δ ) 0.0 ppm) served in phosphorus spectra. Tuning of the probe head, careful homogeneity adjustment, and trial experiment(s) with a few scans were performed before final acquisition. During the test, 14 1H, one HH-COSY (14), and six 31P{1H} spectra were recorded from the test samples, and more than 20 1H and/or 31P{1H} spectra were recorded from authentic reference samples. Seven spectra were recorded as a test of the spectrometer performance. The ROP (6) was followed in the sample preparation: the sample (water or extract) was concentrated, the nondeuterated solvent was changed to the corresponding deuterated one, and dust and other nondissolved particles were filtered out from the sample. Relative to the starting level, as much as 10-fold concentrations could be obtained in the NMR samples. Since the pH affects the chemical shifts of phosphonate monoesters, phosphonic acids, and amines in water, the pH of the authentic reference sample was adjusted to the same value as in the test matrix. The samples of the authentic reference compounds were prepared similarly to the test samples but in higher concentrations. Fourteen NMR samples were prepared from the sample matrices delivered by the test coordinator.
Sample Preparation and Experiments from Extracts E and EB. A 1-mL sample of the extract (E) was taken for NMR. The solution was evaporated nearly to dryness by a gentle flow of nitrogen at room temperature. A 1-mL sample of acetone-d6 (Aldrich >99.8% D) was added, and the solution was re-evaporated to about 0.1 mL. This was repeated. The solution was filtered into a rinsed NMR tube (Wilmad 507-PP or 527-PP) through a cotton plug placed in the neck of a Pasteur pipet. The vial and the filter were rinsed with 4 × 200 µL of acetone-d6. The sample of the extract blank (EB) was prepared in the same way as the sample of E. An authentic reference sample was prepared by dissolving about 36 mg of 2 in 0.8 mL of acetone-d6. The 1H spectra were recorded with flip angle of 90°, a repetition time of 8.0 s, a spectral width of 4673 Hz, and 65 536 points in the time domain. The number of scans was 7168 for the sample prepared of E (Figure 2, middle), 5732 for the sample prepared of EB (Figure 2, bottom), and 16 for the sample prepared of authentic 2 (Figure 2, top). Sample Preparation and Experiments from Waters W-1, W-2, and WB. A 10-mL sample of the water (W-1 or W-2) was taken for NMR. The solution was evaporated with a rotary evaporator (+50 °C, 35 mmHg, ca. 30 min) to about 1 mL and further by a flow of nitrogen at 20-45 °C nearly to dryness. A 1-mL sample of D2O (Merck Uvasol, >99.8% D) was added, and the solution was re-evaporated to about 0.1 mL. These two steps were then repeated. A fine precipitate was formed, and as above, the solution was filtered through cotton plug into an NMR tube. The vial and the filter were rinsed with 4 × 200 µL of D2O. The sample of the water blank (WB) was prepared in the same way as the samples of W-1 and W-2. The pH was 8.9 in the W-1 sample, 8.6 in the W-2 sample, and 8.3 in the WB sample. An authentic reference sample was prepared by dissolving about 3 mg of 3 and 0.3 mg of synthesized 4 in 0.8 mL of D2O (pH 8.8). Three additional reference samples were prepared by dissolving 2 µL of 5 (pH 8.8), 2 µL of 6 (pH 8.8), and 28 mg of synthesized 7 (pH 8.6), separately, in 0.8-mL portions of D2O. The 1H spectra of the W-1 sample (Figure 3, middle), the W-2 sample (Figure 4, bottom), and the authentic samples were recorded with the presaturation pulse sequence (15). The spectra were recorded with a flip angle of 90°, a repetition time of 5.5 s, a spectral width of 4673 Hz, and 32 768 points in the time domain. The number of scans was 4096 for the samples of W-1 and W-2, 6144 for the sample of WB (Figure 3, bottom), 256 for the samples of 3 and 4 (Figure 3, top), 16 for the samples of 5 and 6, and 128 for the sample of 7. The 31P{1H} NMR spectrum of the sample of W-1 was recorded with a flip angle of 90°, a repetition time of 5.0 s, a spectral width of 26315 Hz, and 65 536 points in the time domain. The number of scans was 4096 for the sample of W-1, 1345 for the sample of WB, and 256 for the sample of authentic 3 and 4. Sample Preparation and Experiments from Sands S and SB. A total of 10 g of the sand (S) was extracted by sonication for 2 × 10 min with 2 × 10 mL of distilled water. A 10-mL sample of the solution was taken for NMR and evaporated with a rotary evaporator to about 1 mL. The solution contained a fine precipitate and was filtered through a 0.45µm HPLC filter unit (Millex-HV). The vial and the filter unit were rinsed with a total of 3.5 mL of D2O, the filtrate, and the rinsing solutions were combined and evaporated by a flow of nitrogen at 37-40 °C nearly to dryness, 1 mL of D2O was added, and the solution was re-evaporated to about 0.1 mL. The solution was then filtered into an NMR tube as described above, and the vial and the filter were rinsed with 4 × 200 µL of D2O. The sample of the sand blank (SB) was prepared in the same way as the sample of S. The pH was 8.9 in the sample of S and 8.6 in the sample of SB. The 1H spectrum of the sample prepared of S was recorded with a presaturation pulse sequence with 4096 scans, a flip angle of 90°, a repetition time of 5.5 s, a spectral width of 4673
VOL. 31, NO. 2, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
519
TABLE 1. Structures of Spiking Compounds, Names, Concentrations, and Amounts of Sample Matrices Delivered and Methodsa Used in Identification in Second Trial Proficiency Test Coordinated by OPCW/PTS idenfification method
Eb
Structure, name, and amount spiked O
1
O
P
W-1c
W-2d
Se
NMR IR EI CI
NMRm IR EI CI
NMR IR EI CI
NMRm IR EI CI
NMRg IR EI CI
SCH2CH2N(CH2CH3)2
CH3
O-cyclopentyl S-2-(diethylamino)ethyl methylphosphonothiolate,f approximately 5.4 µg/mL 4 3 1 2 CH3CH2N(CH2CH2Cl)2
2
bis(2-chloroethyl)ethylamine (HN-1),h approximately 5.2 µg/mL (calculated as free base)
NMR IR EI CI NMR IR EI CI
O
3 HO
P
OH
αCH3
methylphosphonic acid,i approximately 10.6 µg/mL NMRk IR EI CI
O 3
4
2
1
O
P
OH
αCH3
cyclopentyl methylphosphonate,i,j approximately 9.8 µg/mL 4 3 1 2 CH3CH2N(CH2CH2OH)2
5
ethyldiethanolamine,l approximately 10.4 µg/mL in W-2; approximately 9.1 µg/g in S 4 3 1 2 (CH3CH2)2NCH2CH2OH
6
diethylaminoethanol; approximately 10.4 µg/mL in W-2; approximately 9.1 µg/g in S 3 4 1 2 SCH2CH2N(CH2CH3)2
7
SCH2CH2N(CH2CH3)2
bis(N,N-diethylaminoethyl)disulfide; approximately 10.3 µg/mL
NMR IR EI CI
a
NMR, 1H (400 MHz) and/or 31P{1H} NMR spectroscopy; IR, GC-FTIR; EI, low-resolution GC-MS/EI; CI, low-resolution GC-MS/CI. E, extract; W, water; S, sand. b Delivered: 4 mL of acetonitrile E; E and the blank (EB) contained 300 µg/mL of diesel fuel. c Delivered: 50 mL of canal water W-1, pH 8.1. d Delivered: 50 mL of canal water W-2, pH 8.1; W-2, but not the blank (WB), contained 10.2 µg/mL of triethylamine (TEA); WB also served as blank for W-1. e Delivered: 50 g of S; S contained 9.1 µg/g of TEA, and S and the blank sand (SB) contained 100 µg/g of polyethylene glycol (average MW 200). f Belongs to Schedule 1.A.3 of the CWC. g Not identified by NMR: the 1H spectrum shows only the methyl resonances. h Belongs to Schedule 1.A.6 of the CWC, spiked as a hydrochloride. i Belongs to Schedule 2.B.4 of the CWC. j In addition, dicyclopentyl methylphosphonate was identified using chemical ionization/tandem mass spectroscopy, GC-FTIR, GC-MS/EI, and GC-MS/CI. k Resonance of H-1 partly overlapped with the hump of the water resonance. l Belongs to Schedule 3.B.15 of the CWC. m Not identified by NMR: resonance of H-2 partly overlapped with the background.
Hz, and 32 768 points in the time domain (Figure 5, second from bottom).
Results and Discussion In general, identifications of compounds were first obtained by GC-MS and then by the other analytical methods. The identifications with NMR were mostly obtained by comparing a spectrum of the test sample with a spectrum of the authentic compound recorded during the test period. On one occasion, the test sample was spiked with the suspected chemical for verification purposes. The compounds identified and the identification methods are set out in Table 1. Identification of Bis(2-chloroethyl)ethylamine 2 in Extract (E). The 1H spectrum of the sample prepared from the extract E (Figure 2, middle) revealed six resonances not present in the blank (Figure 2, bottom). A doublet at 1.713 ppm (15.7 Hz) and a triplet at 0.997 ppm (7.1 Hz) were assigned to the methyl protons of P-CH3 and N-CH2CH3 of 1, respectively. The background overlapped with the rest of the resonances of 1. These data supported the presence of 1, as identified by other methods (Table 1). Four of the resonances agreed in chemical shift and multiplicity with those of authentic 2 (Figure 2, top). The triplet-like resonances at 2.874 and 3.573 ppm were assigned to H-1 and H-2, respectively; the partly overlapped quartet
520
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 31, NO. 2, 1997
at 2.671 ppm was assigned to H-3 (3JH-3,H-4 ) 7.1 Hz), and the triplet at 1.028 ppm was assigned to H-4 (3JH-4,H-3 ) 7.1 Hz). The spectral parameters of authentic 2 were identical except for δH-4 ) 1.027 ppm. On the basis of these data, compound 2 was considered identified by NMR. Identification of Methylphosphonic Acid 3 and Cyclopentyl Methylphosphonate 4 in Water (W-1). Resonances of the spiking compoundsstwo doublets, both with a large coupling (to phosphorus) and several multipletsswere readily found in a spectrum of the sample prepared from the water W-1 (Figure 3, middle) by comparison with the spectrum of the blank (Figure 3, bottom). The doublet at 1.102 ppm (2JH-R,P ) 15.7 Hz) was assigned to H-R of 3, which resonated at 1.092 ppm (2JH-R,P ) 15.7 Hz) in the spectrum of the authentic compounds (Figure 3, top). The phosphorus resonance of 3 was at 21.71 and 21.43 ppm in the test and authentic spectrum, respectively. The doublet at 1.272 ppm was due to H-R (2JH-R,P ) 16.3 Hz) of 4 and was at 1.266 ppm (2JH-R,P ) 16.3 Hz) in the authentic spectrum. The resonance of H-1 overlapped with the hump of the water resonance at 4.66-4.67 ppm. H-2 and H-3, a total of eight protons, showed similar resonance patterns at 1.56-1.85 ppm in the test and authentic spectra. The phosphorus chemical shift of 4 was 26.68 ppm in both
FIGURE 2. Expanded regions of the 400 MHz 1H NMR spectra recorded from a sample prepared from the blank extract EB (bottom), from the extract E (middle), and from authentic 2 (top) in acetone-d6.
FIGURE 4. Expanded regions of the 400 MHz 1H NMR spectra recorded from a sample prepared from the water W-2 (bottom) and from the water W-2 spiked with authentic 7 (top) in D2O.
FIGURE 3. Expanded regions of the 400 MHz 1H NMR spectra recorded from a sample prepared from the blank water WB (bottom), from the water W-1 (middle), and the mixture of authentic 3 and 4 (top) in D2O. The resonance of H-1 of 4 overlaps at 4.66-4.67 ppm with the hump of the water resonance.
FIGURE 5. Expanded regions of the 400 MHz 1H NMR spectra recorded from a sample prepared from the blank sand SB (bottom), from the sand S (second from bottom), from authentic 5 (second from top), and from authentic 6 (top) in D2O.
spectra. On the basis of these data and the similarity of the test and authentic spectra, compounds 3 and 4 were considered to have been identified by NMR. Identification of Ethyldiethanolamine 5, Diethylaminoethanol 6, and Bis(N,N-diethylaminoethyl)disulfide 7 in Water (W-2). Many resonance patterns were present in the proton spectrum recorded from the sample prepared of the water W-2 (pH 8.6) (Figure 4, bottom). More details were obtained in the resolution-enhanced spectrum (not shown), and the HH-COSY spectrum assisted in the assignment of resonances. After other experiments had been carried out, spiking of the test sample with authentic 7 (Figure 4, top) allowed unambiguous assignment of the resonances of 7. Despite the partial overlapping of their resonances, all the spiking compounds (5, 6, and 7) were identified in W-2.
The protons H-1 and H-2 of 5 gave triplet-like resonances at 3.245 and 3.895 ppm, respectively; H-3 gave an overlapped quartet at 3.220 ppm (3JH-3,H-4 ) 7.3 Hz), and H-4 gave a triplet at 1.276 ppm (3JH-4,H-3 ) 7.3 Hz). Corresponding data of authentic 5 (pH 8.8) were δH-1 ) 3.217 ppm, δH-2 ) 3.884 ppm, δH-3 ) 3.190 ppm (7.3 Hz), and δH-4 ) 1.264 ppm (7.3 Hz). The protons H-1 and H-2 of 6 were responsible for tripletlike resonances at 3.286 and 3.909 ppm, respectively; H-3 gave a quartet at 3.269 ppm (3JH-3,H-4 ) 7.3 Hz), and H-4 gave a triplet at 1.305 ppm (3JH-4,H-3 ) 7.3 Hz). The NMR spectral parameters of authentic 6 (pH 8.8) were δH-1 ) 3.271 ppm, δH-2 ) 3.903 ppm, δH-3 ) 3.253 ppm (7.3 Hz), and δH-4 ) 1.299 ppm (7.3 Hz). The triplet-like resonances at 3.053 and 3.422 ppm were attributed to protons H-1 and H-2 of 7, respectively; the quartet at 3.162 ppm was attributed to H-3 (3JH-3,H-4 ) 7.3 Hz), and the triplet at 1.279 ppm was attributed to H-4
VOL. 31, NO. 2, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
521
(3JH-4,H-3 ) 7.3 Hz). The NMR spectral parameters of authentic 7 (pH 8.6) were δH-1 ) 3.039 ppm, δH-2 ) 3.387 ppm, δH-3 ) 3.125 ppm (7.3 Hz), and δH-4 ) 1.265 ppm (7.3 Hz). Triethylamine (Table 1) was not found, probably due to evaporation in the sample preparation. Contribution to the Identification of Ethyldiethanolamine 5 and Diethylaminoethanol 6 in Sand (S). Many resonances not present in the blank spectrum (Figure 5, bottom) were found in the spectrum of the sample prepared from the sand S (pH 8.9) (Figure 5, second from bottom). Triplets near 1.27 ppm, multiplets near 3.20 ppm, and overlapped resonances near 3.87 ppm were assigned to 5 and 6. The resonances of 5 and 6 were broader here than in the spectrum of W-2, however. The triplet-like multiplet of H-1 of 5 was at 3.151 ppm and that of H-2 was at 3.86 ppm; the quartet of H-3 was at 3.119 ppm (3JH-3,H-4 ∼ 7.3 Hz), and the triplet of H-4 was at 1.236 ppm (3JH-4,H-3 ) 7.3 Hz). The resonance of H-2 overlapped with the background. The triplet-like multiplet of H-1 of 6 was at 3.270 ppm and that of H-2 was at 3.90 ppm; the quartet of H-3 was at 3.252 ppm (3JH-3,H-4 ) 7.3 Hz), and the triplet of H-4 was at 1.298 ppm (3JH-4,H-3 ) 7.3 Hz). The resonance of H-2 was almost totally hidden by the background. Figure 5 shows the spectra of authentic 5 (second from top) and 6 (top). In the final NMR report to the Coordinator of the Second Trial Proficiency Test, the presence of 5 and 6 was declared supported. Resonances of triethylamine were not found, and the other additive, polyethylene glycol (Table 1), did not cause overlapping.
Discussion No sensitivity problems were encountered in 1H observation at spiking levels used in this test: 5-10 µg/mL (µg/g) in the original test sample matrices and 6-120 µg/mL in the prepared NMR samples. All problems in compound identification were associated with the overlapping of background resonances. Mutual overlapping of the resonances of 5, 6, and 7 did not prevent their identification. In the case of the NMR sample prepared from the extract (E), however, concentration was too low (about 6 µg/mL) for phosphorus resonances to be seen, even though the background was clean. NMR spectroscopy provided an identification of six (2, 3, 4, 5, 6, and 7) of the seven spiking compounds, and a contribution to the identification of 1 was obtained. In our experience, analyses such as those described here must be performed with special attention paid to the sample preparation and the details of the NMR experiments. Preferably the nondeuterated solvent should be totally replaced by the corresponding deuterated solvent, and the sample should always be filtered before transferring it to a rinsed NMR tube. A particle-free NMR sample provides the best condition for homogeneity adjustment, for narrow lines, and hence for best resolution and sensitivity. The role of blank samples is significant, although obtaining a representative blank from a real target environment admittedly could be difficult. To obtain sufficient signal-to-noise ratio, the experiments may need to last hours or even overnight. The samples prepared from authentic compounds should be similar to the test samples in solvent, pH, and chemical shift reference. For unambiguous identification in uncertain cases, the blank or the test sample should be spiked with the suspected chemical. In cases where insufficient information is obtained, the assigned resonances may provide supporting evidence for the presence of a compound. 1H NMR spectroscopy is a powerful method in the analysis of chemical warfare agents and related compounds present in trace amounts in environmental samples such as water and sand. A high field spectrometer (e.g., at 400 MHz) will generally offer sufficient sensitivity for the detection of chemicals present in trace amounts, but the unknown amount
522
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 31, NO. 2, 1997
and spectral range of the background may cause problems. Use of 31P NMR is limited more by the poor sensitivity than the background. The chemicals shown in Table 1 were identified by at least two methods of analysis, and no false identifications were made.
Acknowledgments The author would like to thank Dr. E. R. J. Wils of the TNO Prins Maurits Laboratory (The Netherlands) for the test samples and the Preparatory Commission for the Organisation for the Prohibition of Chemical Weapons/Provisional Technical Secretariat for organizing the second Trial Proficiency Test. Thanks as well to E-L. Tolppa for assistance during the test and to M-L. Kuitunen, S. Lemettinen, and K. Rosendahl for their expert help in the general sample preparation.
Literature Cited (1) Warning: In view of their toxicity, the compounds classified as chemical warfare agents [in this work: O-cyclopentyl S-2(diethylamino)ethyl methylphosphonothiolate and bis(2-chloroethyl)ethylamine] should be handled only in specialized laboratories. (2) (a) F.1 Testing of Existing Procedures. (b) F.2 Testing of Procedures on Simulated Industry Samples. (c) F.3 Testing of Procedures on Simulated Military Facility Samples. (d) F.4 Validating of Procedures for Water and Soil Samples. F. International Interlaboratory Comparison (Round Robin) Test for the Verification of Chemical Disarmament. In Methodology and Instrumentation for Sampling and Analysis in the Verification of Chemical Disarmament; Rautio, M., Ed.; The Ministry for Foreign Affairs of Finland: Helsinki, 1990-1993. (3) H.1 First Interlaboratory Comparison Test. H. Interlaboratory Comparison Test Coordinated by the Provisional Technical Secretariat for the Preparatory Commission for the Organisation for the Prohibition of Chemical Weapons. In Methodology and Instrumentation for Sampling and Analysis in the Verification of Chemical Disarmament; Rautio, M., Ed.; The Ministry for Foreign Affairs of Finland: Helsinki, 1994. (4) D.1 A Proposal for Procedures Supporting the Reference Database. D.2 Second Proposal for Procedures Supporting the Reference Database. D. Standard Operating Procedures for the Verification of Chemical Disarmament. In Methodology and Instrumentation for Sampling and Analysis in the Verification of Chemical Disarmament; Rautio, M., Ed.; The Ministry for Foreign Affairs of Finland: Helsinki, 1988-1989. (5) Recommended Operating Procedures for Sampling and Analysis in the Verification of Chemical Disarmament; Rautio, M., Ed.; The Ministry for Foreign Affairs of Finland: Helsinki, 1993. (6) Recommended Operating Procedures for Sampling and Analysis in the Verification of Chemical Disarmament; Rautio, M., Ed.; The Ministry for Foreign Affairs of Finland: Helsinki, 1994. (7) An in-house 1H, 13C{1H}, 19F, 31P{1H}, 31P, and 2D NMR Spectrum Library of Chemical Warfare Agents and Related Compounds has been developed. (8) Martin, G. E.; Zektzer, A. S. In Two-Dimensional NMR Methods for Establishing Molecular Connectivity: A Chemist’s Guide to Experiment Selection, Performance, and Interpretation; VCH Publishers, Inc.: New York, 1988. (9) Ref 2d, pp 81 and 209. (10) Ref 3, pp 85-102 and 203-218. (11) Wils, E. R. J.; Hulst, A. G.; Verwiel, P. E. J.; van Krimpen, S. H.; Niederhauser, A. Fresenius J. Anal. Chem. 1992, 343, 297. (12) Mesilaakso, M.; Tolppa, E-L. Anal. Chem. 1996, 68, 2313. (13) Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction; Signed in January 1993; Printed and distributed by the Provisional Technical Secretariat of the Preparatory Commission for the Organisation for the Prohibition of Chemical Weapons. The Depositary of this Convention is the Secretary-General of the United Nations from whom a certified true copy can be obtained. (14) Ref 8, pp 58-71. (15) Derome, A. E. In Modern NMR Techniques for Chemistry Research; Pergamon Press: Oxford, 1987; pp 172-173.
Received for review April 18, 1996. Revised manuscript received September 5, 1996. Accepted September 20, 1996.X ES960352Z X
Abstract published in Advance ACS Abstracts, December 1, 1996.
